What Is Legionnaires' Disease?

American Thoracic Society

PATIENT EDUCATION | INFORMATION SERIES What is Legionnaires’ Disease?

Legionnaires’ disease (also called legionellosis) is an infection of the lung (pneumonia) that can lead to difficulty breathing, respiratory failure or even death. Infectious outbreaks are commonly associated with exposure to water supplies contaminated with Legionella (such as air conditioners).

What causes Legionnaires’ Disease? What are the signs and symptoms of Legionnaires’ Legionnaires’ disease was first described in 1976 disease? when an outbreak infected attendees of the American The signs and symptoms of Legionnaires’ disease are Legion convention. A family of bacteria called similar to other types of pneumonia that are caused by Legionella causes Legionnaires’ disease. The most bacteria. These include: common cause of Legionnaires’ disease is Legionella ■ Shortness of breath pneumophila, but Legionella species other than ■ Cough pneumophila exist and can also cause illness. Legionella bacteria are a part of the environment. They grow best ■ Fatigue in warm water but can also grow in cool water supplies. ■ Decreased appetite Infections have been associated with contamination of ■ Fever the following water sources: CLIP AND COPY AND CLIP ■ Chills ■ Water towers/evaporator condensers ■ Muscle aches (also called ‘myalgias’) ■ Shower heads/faucets ■ Diarrhea ■ Hot tubs ■ Headaches ■ Ultrasonic misters ■ Confusion ■ Humidifiers How is Legionnaires’ Disease diagnosed? ■ Decorative fountains Legionnaires’ disease most commonly causes ■ Plumbing networks pneumonia. Pneumonia is an infection in the lungs Who gets Legionnaires’ Disease? and is diagnosed based on symptoms, physical findings, and results of chest x-ray and blood tests. People are exposed to Legionella by inhaling (breathing Legionella is one of many causes of pneumonia. For in) water droplets that contain the bacteria. Summer more information about pneumonia, please visit www. and early fall are the most common times of the year thoracic.org/patients. for infections to occur. Persons over 50 years of age, who are current or former smokers, those with chronic Your healthcare provider may perform additional diseases such as chronic obstructive lung disease testing to decide if Legionella is the cause of your (COPD) or diabetes, or those with a weak immune pneumonia. These laboratory tests may include: system (immunocompromised) are at a higher risk of ■ Urine test: Legionella has several naturally occurring infection. Of note, Legionnaires’ disease is not passed variations known as ‘species’ and ‘serotypes’. from person to person. Although these differ to some extent, the symptoms

PATIENT EDUCATION | INFORMATION SERIES

they cause are similar. A urine test can detect the Is Legionnaires’ Disease Fatal? presence of the most common disease-causing You can die from severe Legionnaires’ disease. It is serotype, called Legionella pneumophila serotype 1. If estimated that up to 30% of people diagnosed with your urine test is positive for Legionella, then you are Legionnaires’ disease can die due to the infection. believed to have Legionnaires’ disease. The limitation Hence, avoiding exposure is the best way to reduce of this test is that the not all serotypes of Legionella your risk of getting the disease. can be detected using urine testing. This means Can Legionnaires’ Disease Be Prevented? that a “negative” result does not entirely exclude There is no specific vaccine for Legionnaires’ disease. Legionnaires’ disease as the cause of your illness. Hence, the main thing you can do to prevent ■ Culture test: Samples may be collected to culture Legionnaires’ disease is to ensure that different water (grow) the bacteria. The culture samples may be systems that Legionella can grow in, are kept clean. collected from your sputum (also called phlegm or You should avoid exposure to water sources such as mucus) from the lungs. They can also be directly drinking water systems, decorative fountains and hot collected from your lungs, either by placing a scope tubs if you are unsure about their cleanliness. Be sure directly into your airways to collect a sample, that equipment at home such as air conditioners or called “Flexible Bronchoscopy”, or by endotracheal shower faucets are inspected and cleaned often. aspiration, where samples are taken from your lungs when connected to a breathing machine. Rarely, Authors: Chad R. Marion DO, PhD, Charles S. Dela Cruz, MD, cultures from a lung biopsy may be used. A positive PhD, Michael S. Niederman, M.D., MACP, FCCP, FCCM, FERS culture confirms the diagnosis of Legionnaires’ Reviewers: Hrishikesh S Kulkarni, MD, Marianna Sockrider disease. However, these cultures can take many days MD, DrPH to grow, limiting how useful they are to diagnose the disease early. R Action Steps ■ Blood test: Exposure to Legionella induces your immune system to make antibodies (proteins in ✔ Talk with your healthcare provider if you are sick and think you the blood) that recognize the bacteria and help may have pneumonia. clear the infection. Your healthcare provider may ✔ Avoid exposure to water sources that may have Legionella bacteria collect blood to test the level of antibodies at the ✔ Seek immediate medical attention if you have symptoms of time of symptoms and weeks after your recover pneumonia and difficulty breathing. to determine if your immune system produced Healthcare Provider’s Contact Number: antibodies to Legionella. This test is used at times to confirm the diagnosis. It is important to know that if these above tests are “negative” (or do not indicate the presence of Other Resources: Legionella), you may still have Legionnaires’ disease. American Thoracic Society • www.thoracic.org/patients/ How is Legionnaires’ Disease Treated? U.S. Centers for Disease Control Legionnaires’ disease can be treated using an • http://www.cdc.gov/legionella antibiotic. However, not all antibiotics are effective United States Department of Labor against Legionella. It is important that your healthcare • https://www.osha.gov/SLTC/legionnairesdisease/control_ prevention.html provider make the correct diagnosis to ensure that World Health Organization they prescribe an effective antibiotic. However, • http://www.who.int/mediacentre/factsheets/fs285/en/ antibiotics that cover a wide range of bacteria are Medline Plus (National Library of Medicine/ often prescribed until a definite diagnosis is made. National Institutes of Health) • https://www.nlm.nih.gov/medlineplus/legionnairesdisease.html If you are very ill, you may need to be admitted to the hospital. If you develop severe pneumonia, you This information is a public service of the American Thoracic Society. may even need the support of a breathing machine The content is for educational purposes only. It should not be used as a (mechanical ventilator). Please see the Patient substitute for the medical advice of one’s health care provider. Information Series on Mechanical Ventilation at www. thoracic.org/patients.